Ultra high frequency tuner



July 12, 1960 H. c. ROWE 2,945,189

ULTRA HIGH FREQUENCY TUNER original Filed sept'. 21, 1951 4 sheets-sheet1 E/ld 1 116 100 1.94 W 1 112 .a. Y I n` 4 l z-.nwjfi k2? l;z1/)nf0rfda??? I ifo-we.

July 12, 1960 H. c. RowE 2,945,189

ULTRA HIGH FREQUENCY TUNER Original Filed Sept. 21, 1951 4 Sheets-Sheet2 July 12, 1960 H. c. RowE 2,945,189

ULTRA HIGH FREQUENCY TUNER Original Filed Sept. 21, 1951 4 Sheets-Sheet3 1 jl ik I @6 /318 il L 31e 696 .326 l i .R32 I l f6 .376 314 296 320 f382580 "8., #i .354 .324 g" .58 .360 I (310 I I 37I2Iu/ ab@ i a02 ma7".' @Yardfy` 6'. jo we y H* my;

H. C. ROWE ULTRA HIGH FREQUENCY TUNER Grginal Filed Sept. 21, 1951 July12, 1960 4 Sheets-Sheet 4 United States Patent ice ULTRA HIGH FREQUENCYTUNER Harry C. Rowe, Cincinnati, Ohio, assignor to Stewart- WarnerCorporation, Chicago, Ill., a corporation of Virginia Originalapplication Sept. 21, 19151, Ser. No. 247,627,

now Patent No. 2,770,723, dated Nov. 13, 1956. D1- vided and thisapplication Jan. 16, 1956, Ser. No. 563,405

2 Claims. (Cl. 331-98) This invention relates generally to radioapparatus for ultra high frequencies, and particularly to tunabledevices such as oscillators, amplifiers, and modulators. The inventionis especially applicable to combinations of tunable devices. One suchcombination is the tuner section of a superheterodyne radio receiver.The tuner of such a receiver may include radio frequency amplifiers, ahigh frequency oscillator, and a mixer or modulator, al1 of which aretuned concurrently. This application is a division of applicantscopending application, Serial No. 247,627, filed September 21, 1951, nowmatured into Patent 2,770,723, issued November 13, 1956.

An object of the invention is to provide a superheterodyne tuner forcontinuously covering an extremely wide frequency band at extremely highfrequencies. For example,.an object is to cover the frequency band fromapproximately 500 megacycles to approximately 1000 megacycles in onecontinuous range. This particular frequency band is very useful for suchradio services as television. Covering a wide band in one continuousrange eliminates many complications such as band switching.

A further object is to provide an oscillator providing usefulfundamental output in the neighborhood of 1000 megacycles. Such anoscillator is extremely Valuable as the high frequency oscillator of asuperheterodyne tuner. Utilizing the fundamental output of an oscillatorrather than `its harmonic output Iavoids many difficulties, such as thespurious reception of signals at points in a tuning range other than thesingle correct point.

A further object is to provide an ultra high frequency tuner in whichsatisfactory tracking between the high frequency oscillator and theradio frequency .tuning circuits is easily obtained without resorting toa complicated mechanical drive. Tracking involves a tuning scheme formaintaining a fixed frequency difference between the operatingfrequencies of the high frequency oscillator and the radio frequencycircuits of a superheterodyne tuner. A further object is to provide atuning arrangement providing a considerable amount of band spread toavoid critical and diflicult tuning. Band spread involves an arrangementin which a movable tuning member must be moved over a considerabledistance to traverse a fre quency band.

A further object is to provide :an -ultra high frequency tuner which isextremely small and compact. Miniaturization and evensub-miniaturization of apparatus is extremely important in the militaryfield.

. yA further object is to provide an efficient improved tuner utilizingtubes which are readily available and relatively economical.

A further object is to provide a tuner which may be manufactured veasilyand economically.

. Further objects, advantages and features of the invention will becomeapparent from the following description of illustrative embodiments.

In the course of the,

2,945,189 Patented July 12, 1960 description, reference will be made tothe drawings in which:

Fig. 1 is an elevational View of an ultra high frequency tunerconstructed in accordance with the invention;

Fig. 2 is a sectional plan view of the tuner taken as indicated by theline 2 2 of Fig. 1;

Fig. 3 is a sectional side elevational view of the tuner taken asindicated by the line 3 3 in Fig. l;

Fig. 4 is a fragmentary elevational sectional view taken as indicated bythe line 4 4 in Fig. 2;

Fig. 5 is a fragmentary elevational sectional view taken as .indicatedby the line 5 5 in Fig. 2;

Fig. 6 is a fragmentary plan sectional view similar to Fig. 2illustrating a modification of the tuner shown n Figs. 1 to 5;

Fig. 7 is a fragmentary plan sectional view similar to Fig. 2illustrating another modification of the tuner shown in Figs. 1 to 5;

Fig. 8 is an enlarged fragmentary sectional view taken as indicated bythe line 8 8 in Fig. 7;

Fig. 9 is an enlarged fragmentary sectional view taken as indicated bythe line 9 9 in Fig. 7;

Fig. 10 is a sectional plan View of another improved modified tuner,constructed in accordance with the invention;

Fig. 11 is an elevational sectional view taken as indicated by the line11 in Fig. 10;

Fig. 12 is a fragmentary elevational view taken as indicated by the line12 12 in Fig. 10;

Fig. 13 is a sectional plan view similar to Fig. 10 illustrating amodification of the tuner of Fig. 10; and

Fig. 14 `is a fragmentary sectional view taken as indicated by the line14 14 in Fig. 13.

The tuner shown in Figs. l-5 includes an oscillator section 20 and amixer section 22. The oscillator section includes a triode tube 24having a cylindrical plate terminal 26 at one end and a cylindricalcathode terminal 28 at the other end. A pair of tubular glass sections30 and 32 connect the plate and cathode cylinders with a centraldisc-shaped grid terminal 34. The tube 2'4 may be the RCA type 5675.

The oscillator section includes a crystal rectifier 40 having endterminals 42 and 44 in the form of metallic pins. The front terminal 42is tightly fitted or soldered into an apertured internal flange 46inside an elongated cylinder 48 having the same outside diameter as theplate terminal cylinder 26 of the tube 24. The rear terminal pin 44 ofthe crystal rectifier 40 is soldered into an apertured disc 50 havingapproximately the same diameter as the grid disc 34 of the tube 24.

The tube 24 and the crystal rectifier 40 are supported on a rear baseplate 52 with .the plate cylinder 216 -of the tube and the sleeve 48parallel. The grid disc 34 and the disc 50 are positioned 4in generallycircular oversized openings 54 and 56 extending through the insulatingbase plate 52. The front ends of the holes 54 and 56 are partly closedby a pair of metallic coupling plates 58 and `60 secured to the frontside of the base plate 52. Thin sheets 62 and 64 of a dielectricmaterial are positioned in back off the plates 58 and 60 to insulate theplates from the grid disc 34 and the crystal terminal disc 50,respectively.

The grid disc 34, the thin circular plate 58 and the dielectric film l62form a grid blocking capacitor for the oscillator section 20.

The coupling plate 60, the crystal terminal disc 50 and the thininsulating sheet 64 form a blocking capacitor in the mixer circuit 22.

The grid disc 34 is pressed lightly against the insulating sheet 62 by apair of diametrically positioned metallic studs 66 and 68 (Fig. 4)carried by a pair of parallel 1 arms 70 and 72 of a flexible insulatingspider 74. The

crystal terminal disc 50 is lightly pressed against the insulating sheet64 by a pair of studs 76 and 78 carried by arms 80 and 82 which extendin a direction opposite the arms 70 and 72 on the spider 74.

The spider is held in place by a single machine screw 84 threaded intothe base plate 52. The spider is held in alignment with the tubes 24 andthe crystal rectifier 40 by a pair of machine screws 86 and 88 whichregister with -apertures 90 and 92 in the spider. The machine screws 86and 88 also serve to mount the coupling plates 58 and 60 on the baseplate 52. When the machine screw 84 is tightened down the spider 74 exesslightly as shown in Fig. 2 to produce slight pressures on the grid disc34 and the crystal disc 50.

A pair of sleeves 94 and 96 are slidably carried on the plate cylinder26 and the crystal cylinder 48. The sleeves 94 and 96 form parts of apair of tuning circuits 98 and 100 which also include a pair of posts102 and 104 which extend parallel with the plate cylinder 26 and thecrystal 48 respectively. The posts are mounted on the base plate 52 bymeans of machine screws 106 and 108. The rear ends of the posts arethereby clamped into electrical contact with the Ifront surface of thecoupling plates 62 and 64.

A pair of elongated sleeves 110 and 112 are slidably carried by theposts 102 and 104. The sleeves 110 and 94 are joined together by a crossbar 114 and the sleeves 96 and 112 by a cross bar 116.

The sleeve 94, the cross bar 114, the sleeve 110, the post 102 and thecoupling plate 58 are included in the tuning circuit 98 which providescoupling between the plate cylinder 26 and the grid disc 34 of the tube24. The tuning circuit 100, which couples the crystal cylinder 48 withthe crystal terminal disc 50, includes the sleeve 96, the cross bar 116,the sleeve 112, the post 104 and the coupling plate 60.

An insulating drive screw 120 is threaded through the cross bar 114 toprovide means for sliding the sleeves 94 and 110 back and forth on theplate cylinder 26 and the post 102. The screw 120 is rotatably carriedby an insulating front base plate 122 connected with the rear base plate52 by means of four insulating pillars 124. The rear end of the screw120 has a nose portion 124 having a reduced diameter to tit snugly intoa bearing aperture in the coupling plate 58.

A similar insulating screw 126 is threaded through the cross bar 116 toprovide means for sliding the sleeves 96 and 112 back and forth. Thescrews 120 and 126 have flanges -128 and 130 adjacent their front endswhich abut against the front base plate 122 to limit endwise movement ofthe screws.

A pair of coiled compression springs 132 and 134 are positioned aroundthe screw 120 and 126 respectively between the cross bars 114 and 116and a pair of conductive collars 136 and 138 positioned adjacent thefront base plate 122. A pair of terminal washers 140 and 142 arepositioned between the -front base plate 122 and the collars 136 and138. The springs 132 and 134, the collars 136 and 138, and the terminals140 and 142 provide means for making electrical contact with the crossbars 114 and 116. The springs 132 and 134 also take up any endwise playin the drive including the screws 120 and 126.

The screws 120 and 126 may be rotated simultaneously by means of a driveincluding gears 144 and 146 mounted on the front ends of the screws 120and 126. The gears mesh with a pinion 148 which may be rotated manuallyby means of a tuning knob 150.

The studs 66 and 78 provide means for making electrical contact with thegrid dise 34 and the crystal disc 50 respectively. A resistor 152 and achoke 154 may be connected between the studs and a pair of terminal lugs156 and 158.

The heater connections yfor the tube 24 are brought out by means of pins160. A socket 162 may be providedl to make contact with the heater pins160. Heater current may be supplied to the socket by means of a pair ofheater chokes 164 and 166 which are connected between the socket 162 anda pair of terminal lugs 168 and 170 mounted on a terminal strip 172which is supported on the spider 74 by means of a pair of metallicpillars 174 and 176. The pillars provide electrical connections betweenthe terminal lugs 156 and 158 and a pair of terminal lugs 178 and 180carried on the rear side of the terminal strip 172. The pillar 174 alsomakes contact with a lug 182 which is connected by means of a conductor184 to a clip 186 carried on the cathode cylinder 28 of the tube 24.Thus, the grid disc 34 of the tube 24 is connected with the cathodecylinder 28 by means of the stud 66, the resistor 152, the pillar 174,the conductor 184, and the contacting clip 186.

A collar 188 is snugly carried on the cathode cylinder 28 above thecontacting clip 186. The collar has a ange 190 which carries a pluralityof wires 192 which extend generally parallel with the tube 24 throughclearance holes 193 in the grid disc 34. The front ends of the wires 192are positioned adjacent the rear end of the plate cylinder 26. Theassembly including the collar 188, the flange 190 and the wires 192provides supplementary capacitance between the plates 26 and the cathode28.

A coupling loop 194 having a single turn is mounted on the rear baseplate 52 adjacent the tuning circuit 100 in order to provide means forimpressing an input signal upon the mixer section 22.

Supplementary coupling between the mixer section 22 and the oscillatorsection 20 is provided by means of plates 196 and 198 which arepositioned adjacent the plate cylinder 26 and the crystal cylinder 48respectively. The plates are connected together by means of a rigidconductor 200 which is mounted on the rear base plate 52 by means of aninsulating bracket 202.

Operation of the apparatus of F igs. 1-5

To put the tuner into operation, plate voltage is applied between thelug and the cathode terminal 178. The plate current is conducted to thecylindrical anode terminal 26 through the coil spring 132. Heatervoltage is applied between the terminals 168 and 170. The resistor 152provides grid bias for the tube 24. Input signals from an antenna or aradio frequency amplier stage may be applied to the coupling loop 194.The output of the tuner may be taken between the terminal and the lug142. The terminal 180 is connected to one side of the crystal 40 throughthe choke 154, and the lug 142 is connected to the other side of thecrystal through the coil spring 134.

Feedback to produce oscillation in the oscillator section 20 is providedby the tuning circuit 98, which couples the plate cylinder 26 of thetube 24 with the grid disc 34. The grid disc 34, the coupling plate 58and the dielectric film 62 form a grid blocking capacitor connecting oneend of the tuning inductance 98 with the grid of the tube 24.

The tuning circuit 98 has a relatively large value of inductivereactance at the resonant frequency. The main resonant circuitcapacitance is that of the internal capacitance between the plate andthe grid of the tube 24.

The conductors 192 provide supplementary capacitance between the cathodeand the plate of the tube 24. The supplementary capacitance is extremelyimportant for promoting oscillation in the oscillator section 20. Thesupplementary capacitance provides a proper relationship between theplate-to-cathode and the grid-to-cathode voltages in the oscillatorsection, both as to phasing and magnitude. The tube 24 has a relativelylow plate-tocathode capacitance with respect to its grid-to-cathodecapacitance. The additional plate-to-cathode capacitance, provided bythe conductors 192, improves the division of high frequency voltagesbetween the plate-to-grid path and the grid-to-cathode path of the tubeZ4.

Signals impressed upon the coupling loop 194 are transmitted inductivelyto the tuning circuit 100 of the mixer section 22. The tuning circuitimpresses the signals between the terminals of the crystal rectifier 40.The crystal terminal disc 50, the coupling plate 60, and the dielectricfilm 64 provide a blocking capacitor to avoid shortcircuiting thecrystal rectifier 40. The tuning circuit 100, which is largelyinductive, is resonated by its own distributed capacitance, thecapacitance between the crystal terminal disc 50 and the crystalcylinder 48, and the internal capacitance between the terminals of thecrystal 40.

The close proximity of the oscillator section 20 and the mixer section22 provides inductive and capacitive coupling to transmit signals fromthe oscillator section 20 to the mixer section 22. The plates 196 and198 provide supplementary capacitive coupling between the oscillatorsection 20 and the mixer section 22.

The operating frequency of the oscillator section 20 may be varied byshifting the position of the slide bar 114 and the sleeves 94 and 110carried by the bar. The primary effect of moving the sleeves 94 and 110'along the plate cylinder 26 and the post 102 is to change the inductanceof the tuning circuit 98, although the distrib- 'uted capacitance of thetuning circuit is also changed to a certain extent. Moving the slide bar114 inwardly reduces the physical length and the inductance of thetuning circuit 98, and thereby raises the operating frequency of theoscillator 20.

The resonant frequency of the mixer tuning circuit 100 'is changed byshifting the sleeves 96 and 112 along the terminal cylinder 48 and thepost 104. Since the oscillator section 20 and mixer section 22 are tunedby a straight line sliding movement, the arrangement to provide gangedtuning of the oscillator and the mixer is quite simple. The oscillator20 and the mixer 22 are tuned simultaneously by turning the knob 150.The knob is geared to the oscillator and mixer drive screws 120 and 126,which are threaded through the slide bars 114 and 116.

The operating frequencies of the oscillator 20 and the mixer 22 arevariable from about 500 megacycles to about 1000 megacycles. Of coursethe oscillator and the mixer are tuned to frequencies which differ bysome constant intermediate frequency. However, the frequency differenceis quite small, since the intermediate frequency is only a smallfraction of the operating frequency of the mixer section 22. Thedifference in the operating frequencies of the tuning circuits 98 and100 may be adjusted merely by shifting one of the drive screws 120 or126 with respect to its driving gear 144 or 146.

Inasmuch as the oscillator operates at the fundamental frequency and theintermediate frequency is small compared to the oscillator frequency,the tuning circuits 98 and 100 are substantially alike. Hence, theproblem of tracking these two circuits to operate at the constantdifference of the intermediate frequency `by mechanical deviation meansis much more simple. The crystal terminal cylinder 48 and the crystalterminal disc 50 provide an arrangement which corresponds closely withthe physical configuration of the oscillator tube 24.

The tuning circuits 98 and 100 provide low inductance values to resonatein the range from 500 to 1000 megacycles. Nevertheless the circuits 98and 100 have exceptionally low losses and high factors of merit.Operation of the oscillator 20 in the neighborhood of 1000 megacycles ispossible only because of the low loss construction of the tuning circuit98. Arranging the sleeve 94 to slide directly on the anode terminalcylinder 26 provides a minimum of losses fromA such factors as contactresistance and dielectric losses in insulating supports.

The construction of the tuned circuits 98 and 100 is such that lossesfrom contact resistance are negligible. The coupling between the sleeves94, 110, 96 and 112 and the cylinders 26, 102, 48 and 104 is largelycapacitive rather than conductive. Each of the sleeves is so long thatthe capacitive reactance between the sleeve and its cylinder is muchsmaller than the contact resistance between the sleeve and the cylinder.The provision of the capacitive coupling in shunt with the slidingcontacts eliminates any substantial possibility of noisy operation dueto contact imperfections. Furthermore, by virtue of the capacitivecoupling the sleeves may be fitted freely on the cylinders so that thesleeves may be shunted smoothly without binding. A free sliding iitbetween the sleeve 94 and the anode cylinder 26 is particularlyimportant because excessive friction between these parts might damagethe glass portions 30 and 32 of the tube 24.

The tube 24 and the crystal 40 are mounted in such a way that they mayshift laterally as the sleeves 94 and 96 are moved along the cylinders26 and 48. This mounting arrangement prevents binding between thesleeves and the cylinders. Such binding might damage the tube 24 or thecrystal 40. The holes 54 and 56 in which the grid disc 34 and thecrystal disc 50 are positioned are oversized to permit lateral movementof the discs. The discs are held in place only by light pressure appliedby the spider 74. The leads which make electrical connection with thetube 24 have sufficient excess length to permit lateral shifting of thetube.

Utilizing the anode terminal cylinder 26 as a support for the slidablesleeve 94 provides a particularly compact and economical tuning circuithaving a minimum number of parts. This constructional feature is largelyresponsible for the subminiature proportions of the tuner.

The coil springs 132 and 134 take up any slack between the drive screwsand 126 and the slide bars 114 and 116. The coil springs also serve ashigh frequency choke coils to make electrical connections to the slidebars without interfering with the operation of the oscillator 20 or themixer 22. The springs 132 and 134 are wound with enough turns tofunction eiiciently as choke coils. As the oscillator and the mixer aretuned, the length and the inductance of the springs change, the lengthbecoming greater and the inductance smaller as -the operating frequencyof the tuner increases, and vice versa. This variation in the length ofthe springs automatically chan-ges the inductance of the springs as theoperating frequency of the tuner changes, so that the inductance ismaintained approximately at an optimum value.

The tuning circuits 98 and .100 provide a considerable amount ofbandspread. This arises from the fact that the slide bars 114 and 116are movedl a considerable distance as the tuning range is traversed.

Apparatus of Fig. 6

The modification illustrated in Fig. 6 is quite similar to a portion ofthe apparatus of Figs. 1-5 and corresponding components have been giventhe same reference characters in the various figures. A modifiedoscillator section 220 is illustrated in Fig. 6. However, it should beunderstood that the modifications are also applicable to the mixersection of the tuner. The oscillator section 220 includes a tunedcircuit 222 which is somewhat simillar to the tuned circuit 98 exceptthat an additional post 224 is provided. The post 224 is secured to therear mounting plate 52 by means of a machine screw 226. The post 224 isthereby clamped into electrical contact with the coupling plate 58 at apoint dametrically opposite from the post 102.

A sleeve 228 is slidable along the post 224. The sleeve 228 is connectedwith the sleeves 94 and 110 by means of a cross bar 230. Means isprovided to move the cross bar 230 backward and forward for tuning theoscillator, the means including an insulating bar 232 connected with thecross bar 230 by a pair of insulating pillars 234 and 236. A drive screw238 is secured to the Vcenter of the insulating bar 232. The drive screw238 is aligned with the axis of the tube 24.

Plate supply voltage may be applied to the tube 24 through a highfrequency choke coil 240 which is connected by means of a clip 242 to agenerally cylindrical nose 244 protruding axially from the platecylinder 26. The nose 244 is electrically connected with the platecylinder 26.

The additional post 224, the sleeve 228, and the righthand portion ofthe cross bar 230 provide an additional turn in parallel with the turnprovided by the post 102 and the sleeve 110. Thus the tuned circuit 222has a smaller inductance than the tuned circuit 98 of Fig. 2, assuminglthat corresponding dimensions of the two tuned circuits are the same.The tuned circuit 222 has a somewhat higher Q (factor of merit) than thetuned circuit 98.

Apparatus of Figs. 7-9

A further modification is illustrated in Figs. 7-9. This modification isalso quite similar to a portion of the apparatus of Figs. 1-5 andcorresponding parts have been given the same reference characters. Fig.7 illustrates a modified oscillator section 250. However, again itshould be understood that the modifications are applicable to the mixersection of the tuner. The oscillator section 250 includes a cylindricalcup 252 which is secured to the rear mounting plate 52. The grid disc 34of the tube 24 directly contacts the cup 252, the insulating sheet 62being omitted in this embodiment. The cup 252 has an axial aperture 254which clears the tube 24 and the conductors 192.

The cup 252 together with a telescoping cup 256 forms a tuned circuit258. An axial sleeve 260 secured to the cup 256 is slidable along theplate cylinder 26 of the tube 24. However, the sleeve 260 iselectrically insulated from the plate cylinder 26 by means of aplurality of spacer rods 262 interposed between the sleeve and thecylinder 26. The cup 256 is electrically insulated from the cup 252 bymeans of a plurality of spacer rods 264. Plate voltage is supplied tothe plate cylinder 26 by means of the choke coil 240, as described inconnection with Fig. 6.

An insulating bar 266 is secured to the cup 256 by means of insulatingpillars 268 and 270. A drive screw 272 may be carried by the center ofthe bar 266 to provide means for varying the extent to which the cups252 and 256 are telescoped.

The telescoping cups 252 and 256 provide a toroidal tuned circuit whichis primarily inductive. The tuned circuit 258 is resonated by its owndistributed capacitance and the internal capacitance between the anodeand the grid of the tube 24. The tuned circuit 258 provides a feed-backpath from the anode to the grid of the tube 24. The operating frequencyof the oscillator section 250 is varied by changing the extent to whichthe cups are telescoped', the frequency increasing as the cups are movedtogether. During tuning the sleeve 260 slides along the anode terminalcylinder 26.

The capacitance between the closely spaced cups 252 and 256 obviates anyneed for electrical contact between them. Likewise the capacitancebetween the sleeve 260 and the anode cylinder 26 makes `directelectrical contact unnecessary. The elimination of sliding electricalcontacts avoids any possibility of noisy operation during variation ofthe tuned circuit 258. Since the cup 252 is completely insulated fromthe anode cylinder 26, there is no need for a separate grid blockingcapacitor. The capacitance between the cups serve this purpose.

The toroidal inductor 258 formed by the telescoping cups 252 and 256 hasan extremely high figure of merit or Q. The magnetic field produced bythe tuned circuit 258 is largely confined to the space within the cups252 and 256.

Comparison of the various modifications of Figs. l9

It will be recognized that the tuned circuit 258 of Fig. 7 represents anultimate development of the tuned circuit 98 of Fig. 2. The couplingplate 58, the post l102, the sleeve 110, the cross-bar 114, and thesleeve 94 represent an elemental segment of a toroidal tuned circuitsuch as the tuned circuit 258 of Fig. 7. Fig. 6 represents anintermediate development having two elements of a toroidal tunedcircuit.

All of the embodiments of Figs. l to 9 include timed circuits which arevariable by sliding a sleeve along an anode terminal cylinder of anelectron tube, or along a terminal cylinder of some other circuitcomponent for utilizing high frequency signals.

Apparatus of Figs. 10-12 Figs. 10, 11 and 12 illustrate a modifiedoscillator section 290 of a tuner. Many of the constructional featuresillustrated in these iigures are also applicable to a mixer section of atuner.

The oscillator 290 of Fig. 10 includes a triode tube 292 having an anodeterminal in the form of a cylindrical cap 294. A metallic disc 296positioned behind the cap 294 is also connected to the anode of the tube292. The grid terminal of the tube 292 is in the form of a disc 298concentric with the disc 296 and spaced therefrom by a glass tubularsection 300. The disc 298 has a larger diameter than the disc 296.

The tube 292 has a metallic shell 302 which is concentric with the disc298 and is spaced therefrom by a tubular glass section 304. The shell302 has a larger diameter than the disc 298. The shell 302 is coupled tothe cathode of the tube 292 by capacitance inside the tube. Thus theshell 302 4is a cathode terminal for high frequency currents. Thecathode and heater connections to the tube 292 are brought out throughbase pins which may be contacted by means of a socket 305. The tube 292may be a commercial type 2G40. Tubes of this general coniiguration areusually known as lighthouse triodes.

The shell 302 of the tube 292 is positioned in an opening 306 in aninsulating rear mounting plate 308. The tube 292 is secured to the plate308 by means of a ring clamp 310.

An insulating front mounting plate 312 is connected with the rearmounting plate 308 by means of four insulating pillars 314. A metal disc31-6 is secured to the front mounting plate 312 by means of a pair ofinsulating pillars 318. The. anode terminal disc 296 electricallycontacts the disc 316, and the anode terminal cap 294 extends through acentral aperture 320 in the disc 316.

A metallic disc 322 is spaced behind the disc 316. The disc 322 iscarried in this position by a plurality of wire loops 324, which havetheir ends soldered or welded to the peripheries of the discs 316 and322. Twelve equally spaced radial wire loops 324 are illustrated. Theloops together constitute an annular tuning inductor 326.

The tuning inductor is resonated primarily by the capacitance betweenthe discs 316 and l322. The capacitance between the discs may be variedby changing the spacing between them. For this purpose four insulatingrods 330 extend through clearance holes 332 in the disc 316. Projectingnoses 334 at the rear ends of the rods 330 iit in correspondingapertures in the rear disc 322. Rearward thrust is applied to the rods330 by means of an insulating disc 336 connecting the front ends of therods. A metallic drive screw 338 is rotatably carried in a centralaperture 340 in the disc 336. The drive screw is threaded through ametallic bushing 342 carried by the front plate 312. Thus the spacingbetween the plates 316 and 322 may be increased by advancing the drivescrew 338. The wire loops 324 are conformed to urge the disc 322 towardthe disc 316. Consequently the resiliency of the wire loops 324 movesthe discs 322 and 316 together when the drive screw 338 is backed off.

aimais@ The tubular glass section of the tube 292 extends through aclearance hole 350 in the disc 3t22. The disc 322 is spaced from a disc352 which contacts the grid terminal disc 293. Ihe disc 352 is mountedon an insulating disc 354 by means of insulating pillars 356.

The insulating disc 354 is connected with the rear mounting plate 308 bymeans of insulating pillars 358. The glass section 304 extends through aclearance opening 360 in the insulating disc 354. The insulating disc354 'is sufficiently flexible to provide for the maintenance of contactpressures between the discs 316 and the anode terminal disc 296 and alsobetween the disc 352 and the grid terminal disc 298.

Anode voltage may be applied to the tube 292 by means of a highfrequency choke coil 362 connected between a terminal lug 364 mounted onthe front mounting plate 312 and a clip 366 mounted on the anodeterminal cap 294.

Additional capacitance is provided between the anode and the cathode ofthe tube 292 by means of a conductor 370 which is secured to the ringclamp 310. The conductor 370 passes through a hole 372 in the insulatingdisk 354 and a clearance hole 374 in the insulating disc 322. Theconductor 370 includes a front end portion 376 which is bent over toextend generally parallel with the disc 316. A plurality of conductors370 may be provided for greater symmetry, if desired.

A grid biasing resistor 380 is connected between the disc 352 and aterminal lug 382 mounted on the rear mounting plate 308. The terminallug 382 is connected to the cathode terminal 384 of the socket 305 bymeans of a conductor 386. Heater current may be supplied to the tube 292by means of a pair of heater chokes 388 and 390 connected to the heaterterminals of the socket 305.

The capacitance between the discs 322 and 352 provides coupling betweenthe disc 322 and the grid terminal 298. The tuning inductance 326 isresonated by means of its own distributed capacitance and thecapacitance between the grid and the anode of the tube 292, in additionto the capacitance between the discs 316 and 322.

The tuned circuit including the tuning inductance 326 provides feedbackfrom the anode to the grid of the tube 292. The conductor 370 providessupplementary capacitance between the cathode and the anode of the tube292 in order to improve the division of high frequency voltages betweenthe anode to grid path and the grid to cathode path of the tube.Supplementary capaci- 'tance is usually desirable because the internalanode to cathode capacitance of the tube 292 is usually considerablylower than the internal grid to cathode capacitance.

The inductance of the tubing inductor 326 is relatively low because ofthe large number of wire loops 324 which make up the inductor 326. The Qof the inductor 326 is relatively high. Because of the toroidalconfiguration of the inductor its magnetic field is largely concentratedwithin the wire loops 324.

Apparatus of Figs. 13 and 14 The modification of Figs. 13 and 14 isquite similar t the embodiment of Figs. l0 through 12, and correspondingparts have been given the same reference characters.

In the embodiment of Figs. 13 and 14, a tuning inductor 400 replaces thetuning inductor 326 of Fig. l0. The tuning inductor 400 is in the formof a single continuous sheet metal toroidal turn having its endsconnected to the discs 316 and 322. The inductor 400 ris conformed sothat its resiliency urges the disc 322 toward the disc 316. In otherrespects the embodiments of Figs. 13 and 14 may be the same as theembodiment of Figs. l0 through 12.

The sheet metal toroidal tuning inductor 400 provides a somewhat lowerinductance and a somewhat higher Q than the tuning inductor 326 of Figs.10 and 11. Moreover, the magnetic field of the tuning inductor 400 isvery largely confined within the inductor.

Comparison of the various embodiments All of the embodiments includetuned circuits having toroidal inductive elements. The embodiments ofFigs. 7 and 13 provide different forms of complete toroidal inductors.In the embodiment of Fig. 7 the resonant frequency of the tuned circuitis varied -by changing the inductance of the toroidal coil. In theembodiment of Fig. 13 the resonant frequency is varied chiey by changingthe capacitance connected across the toroidal coil 400. The tuninginductance coils of the embodiments of Figs. 2, 6, and 10, include oneor more elements of a complete toroidal coil.

Each of the embodiments includes an arrangement in which a tuned circuitis advantageously combined with an electron tube having coaxialterminals. The electron tube may be replaced by some other element, suchas a crystal rectifier, for utilizing high frequency signals. Many ofthe embodiments illustrate how advantageously a toroidal tuninginductance may be combined with a signal utilizing element, such as atube, having coaxial terminals.

All of the oscillators illustrated may readily be converted intoamplifiers by coupling one end of the tuning inductance to the grid ofthe tube and the other end to the cathode. In the embodiments of Figs. 1to 9 the conversion from an oscillator to an amplifier may readily bemade merely by tuning the tube 24 end-for-end so that the cathodecylinder 28 rather than the anode cylinder 26 is positioned inside thetuning sleeve 94 or 260. The tube 24 is then operated as a grounded gridamplifier. Of course, appropriate power supply connections are made tothe anode, the cathode and the grid.

Many of the details of the embodiments described above are merelyillustrative and should not be taken as limitative. The invention may bepracticed in many equivalent arrangements. The scope of the invention isindicated by the following claims.

I claim:

1. In an ultra high frequency tuner, an electron oscillator tube havinga plate cylinder and a coaxial grid disc, a first cylindrical cup havingits closed end positioned adjacent the grid disc, a second cylindricalcup telescoping with the first and insulated therefrom, and a sleevecarried aXially by the second cup and slidably positioned on the platecylinder, and means insulating said sleeve from said plate cylinder. i

2. In a high frequency tuner, a signal utilizing element having aterminal cylinder and a coaxial second terminal, a variable inductanceelement connected between the second terminal and the terminal cylinder,the inductance element including a pair of telescoping cups, an axialsleeve mounted on one of the cups and slidably carried on the terminalcylinder, a first insulating spacer positioned between the cups, and asecond insulating spacer positioned between the sleeve and the terminalcylinder, the spacers preventing direct electrical contact between thcups and also between the sleeve and the terminal cylinder, the cupsbeing coupled together and the sleeve being coupled to the terminalcylinder by the respective capacitances between them.

References Cited in the tile of this patent UNITED STATES PATENTS2,167,201 Dallenbach July 25, 1939 2,525,806 Kumpfer Oct. 17, 19502,693,538 Reed Nov. 2, 1954 2,730,623 Emurian et al. Ian. 10, 1956FOREIGN PATENTS 511,795 Great Britain Aug. 24, 1939

